1. Field of the Invention
The present invention relates to a fabricating process of plasma display panel (PDP). More particularly, the present invention relates to a method for forming a phosphor layer on a shadow mask of a PDP utilizing electrophoretic deposition.
2. Description of the Related Art
Referring to FIG. 1, a PDP includes essentially a front substrate 11, a rear substrate 10 and a shadow mask 12 between the front and rear substrates 111 and 10. Each of the front and rear substrates 111 and 10 includes parallel electrodes and a dielectric layer 124 covering the electrodes, and the shadow mask 12 is a grid-like mask with regularly arranged apertures 13, wherein each aperture 13 defines a discharging unit between the front and rear substrates 111 and 10. A phosphor layer 123 is coated on four internal walls of each aperture 13 and the surface of the dielectric layer 124 exposed by the aperture 13 for emitting light.
The conventional method for forming the phosphor layer 123 is screen-printing. However, screen-printing is quite complicated and has the following drawbacks depending on the step sequence. If the shadow mask 12 is printed with the phosphor 123 before being fixed onto the rear substrate 10, the shadow mask 12 is difficult to immobilize as being printed. Meanwhile, since the apertures 13 on the shadow mask 12 are all through holes, the phosphor 123 at the bottoms of the apertures 13 easily falls off after the printing operation to cause the adjacent phosphor to peel off. If the shadow mask 12 is fixed onto the rear substrate 10 before being printed with the phosphor 123, the shadow mask 12 is also difficult to immobilize as being printed. Therefore, the shadow mask 12 is easily shifted as being printed to result in the color mixing problem. Moreover, the phosphor 123 cannot be printed uniformly onto the shadow mask 12.
In addition, because the phosphor for screen-printing is prepared in the form of slurry, a calcination step is required to remove the solvent from the slurry after the printing step. However, since the thermal expansion coefficients of the shadow mask 12 and the rear substrate 10 are different, a misalignment problem frequently occurs after the calcination step to lower the yield and increase the manufacturing cost.